In the prior part, various proposals have been made in order to enhance outputs of a jet propulsion engine such as a turbojet engine, turbofan jet engine, a turboshaft engine, a ram-jet engine or an air turbo ram-jet engine and gas turbine. As an example of the proposals, an advanced turboprop engine (hereinafter referred to as an ATP) to have a bypass ratio of about 40 to 50 has been proposed (see page 16 and the like of "THE JET ENGINE" written by Rolls-Royce pic, publication of Japan Air Technical Association Co.) As shown in FIG. 14, for example, it has been planned that the ATP has a structure in which a gas flow section G is provided on a central portion side and contrarotating propeller blades 51 and 52, that is, air flow section A are provided on the outside of gas flow section G (see Gatzen. B. S & Reynolds, C. N.; I.C.A.S Paper ICAS-84-5.6.2(1984)).
As is well known, the outputs of the jet propulsion engine and gas turbine can also be enhanced by increasing an engine speed. Consequently, it is desirable that an engine speed of the ATP should be increased as much as possible.
As described above, however, the ATP has the gas flow section G formed on the central portion side. For this reason, a hot section is present on the central portion side. Consequently, the engine speed is determined by a material strength against centrifugal force acting on that portion. In other words, there is a problem that the engine speed is limited. Currently, a width of a blade such as a propeller tends to be increased, which results in that the above mentioned problem is being promoted still more.
In an axial-flow compressor, if a pressure ratio in a single stage exceeds about 1.5, a shock wave S is generated between adjacent moving blades M and M provided in a moving blade line as shown in FIG. 15. In general, the shock wave S is generated from a leading edge of a lower surface (pressure surface) of the moving blade M to an intermediate portion of an upper surface (suction surface) of the adjacent moving blade M as shown. In the downstream of the shock wave S, accordingly, an air flow (a boundary layer) separates from the upper surface of the blade. Therefore, performance of the compressor is lowered.
In order to solve the problems according to the prior art, it is an object of the present invention to provide a structure of an output section of a jet propulsion engine or a gas turbine which has a gas flow section provided on a central portion side and an air flow section provided on an outside of the gas flow section, characterized in that centrifugal force acting on the gas flow section is reduced so that an engine speed can be enhanced more than in the prior art.
In order to achieve the above-mentioned object of the present invention, a concept of boundary layer control to be used to prevent a boundary layer from separating from a blade surface and stalling in a lower speed region is applied, in an aircraft, to the structure of the output section of the jet propulsion engine or the gas turbine in a supersonic region.